AIM Block 13 Practice Test 2026 - Free Practice Questions and Study Guide

When starting a turbine engine, you expect the engine to accelerate from the starter's initial spin up to a stable idle speed. A hung start happens when the engine cannot reach that self-sustaining idle RPM. In other words, the engine stays at a low speed or stalls before it can reach idle, so it never becomes self-sustaining with proper fuel and airflow.

This is why the statement “fails to reach idle RPM” is the best answer. It captures the defining fault of a hung start—the inability to achieve the idle condition necessary for normal operation. Other signs like strong vibration or needing more fuel can occur for various reasons, but they don’t specifically identify a hung start.